1. Field of the Invention
This invention relates to a method for using cupric ions as a catalyst to produce salts of monoperoxysulfuric acid. This invention also relates to a method for using cupric ions as a catalyst to simultaneously generate monoperoxysulfuric acid salts and bleach pulp.
2. Description of Related Art
Strong oxidizing agents such as monoperoxysulfuric acid salts are used in producing organic chemicals, treating industrial wastes, bleaching textiles and wood pulps, and as ingredients in cleaning powders and cleansing solutions. A number of U.S. patents disclose processes for making salts of monoperoxysulfuric acid, as exemplified by the following.
U.S. Pat. No. 2,955,020 to Darbee et al. discloses forming monopersulfates using a catalytic amount of a strong inorganic acid. U.S. Pat. No. 4,049,786 to Chiang discloses preparation of a high strength peroxymonosulfate by adding concentrated sulfuric acid to a solution of a soluble peroxydisulfate whereby the heat of solvation of the sulfuric acid hydrolyzes the peroxydisulfate to the peroxymonosulfate. U.S. Pat. No. 3,900,555 to Jourdan-Laforte discloses a process for obtaining monopersulfuric acid from hydrogen peroxide and sulfuric acid. U.S. Pat. No. 3,036,885 to Muller et al. discloses a process for the production of peroxysulfuric acid salts by reacting hydrogen peroxide and a persulfate in the presence of sulfuric acid and water. U.S. Pat. Nos. 2,901,318 and 2,901,319 to D'Addieco disclose processes for producing potassium monopersulfate by reacting a monopersulfuric acid solution containing sulfuric acid with a potassium compound of the group consisting of carbonate, bicarbonate and hydroxide. Crystallization of the potassium monopersulfate from aqueous solutions yields a stable monohydrate. U.S. Pat. No. 2,899,272 to Flach et al. discloses producing a metal persulfate by reacting an aqueous solution of ammonium persulfate and a metal hydroxide. U.S. Pat. Nos. 2,886,412 and 2,886,534 to Lake et al. disclose producing a dry, free-flowing monopersulfate product by adding a boron compound to an aqueous solution of an alkali metal monopersulfate, and thereafter drying the resulting solution. U.S. Pat. No. 2,802,722 to Stephanou discloses producing a solid monopersulfate by reacting monopersulfuric acid, a hydroxide, and a carbonate.
Unfortunately, such processes heretofore have had drawbacks such as low efficiency, high complexity, or high expense.
Recently, however, researchers found that a strong oxidizing agent can be produced by adding calcium or sodium sulfite to vigorously aerated water. Devuyst et al., An Oxidant of Unexpected Utility, Chemtech., 9(7): pp. 426-427(1979). Such work is of interest because it is desirable to cheaply produce a nonchlorine-containing strong bleaching agent for wood pulps. Chlorine and chlorine compounds, although currently much used in bleaching, lead to bleach spent liquor disposal difficulties because the resultant chlorinated organic materials are mutagenic and very darkly colored.
Surprisingly, it has been discovered that the reaction between calcium or sodium sulfite and aerated water to produce monoperoxysulfate can be catalyzed by cupric ions. It has further been discovered that cupric ions can be used to catalyze the generation of monoperoxysulfuric acid salts in situ in a reaction mixture containing pulp, thereby simultaneously bleaching the pulp.